The Apache Point Observatory Galactic Evolution Experiment ( APOGEE ) provides the opportunity to measure elemental abundances for C , N , O , Na , Mg , Al , Si , P , K , Ca , V , Cr , Mn , Fe , Co , and Ni in vast numbers of stars .
We analyze the chemical abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy ( Sgr ) .
This is the largest sample of Sgr stars with detailed chemical abundances and the first time C , N , P , K , V , Cr , Co , and Ni have been studied at high-resolution in this galaxy .
We find that the Sgr stars with [ Fe/H ] \gtrsim -0.8 are deficient in all elemental abundance ratios ( expressed as [ X/Fe ] ) relative to the Milky Way , suggesting that Sgr stars observed today were formed from gas that was less enriched by Type II SNe than stars formed in the Milky Way .
By examining the relative deficiencies of the hydrostatic ( O , Na , Mg , and Al ) and explosive ( Si , P , K , and Mn ) elements , our analysis supports the argument that previous generations of Sgr stars were formed with a top-light IMF , one lacking the most massive stars that would normally pollute the ISM with the hydrostatic elements .
We use a simple chemical evolution model , flexCE to further backup our claim and conclude that recent stellar generations of Fornax and the LMC could also have formed according to a top-light IMF .